@oclair
This is typically due to a plugin/theme conflict.
Try these:
First, try accessing the back end with a different browser and see if the issue persists.
Also, you can test for a plugin conflict by using the Health Check & Troubleshooting plugin. Once activated, click Troubleshoot underneath the Wordfence plugin in the plugins section. Your site’s backend will then act as if just Wordfence is enabled. You can disable Troubleshooting mode via the top admin bar on the site.
Alternatively, instead of using Health Check, you can disable the other plugins on the site one at a time if you’re able to do so.
If you notice no change, I would recommend a reinstall to see if that does it.
Also, be sure to check your browser’s console on the Live Traffic page and look for errors in red. (https://www.wordfence.com/help/advanced/troubleshooting/#how-to-inspect-the-browser-console)
Scott